You ever say something to a person and they asked you a question you thought had an obvious common knowledge answer to before?

Recently someone asked me what an anti theist was. I...I know what it is. I kinda am one but, I had no idea how to answer the question when asked lol. I sorta assumed everyone knows what theists are and just add the word anti in front of it and..uhh..

This is just one example of course, but there are many times when I thought something had an easy obvious answer to that someone still had asked the question.

What are some of the questions people have asked you that you once believed everyone of that age or whatever pretty much already knew the answer too? Were you surprised to hear the question? How did you answer them?

Side note
lulz. I tell people here I am an atheist and they are more or less...Meh! Have no idea what anti theists are, drink almost more than anyone else in the country, no sales tax, and best of all...our cheese is sum o da best in the world!

Anti-theists are different from Atheists.
Atheists just don't believe in God. Anti-theists are opposed to theism. You can be an Atheist but not an anti-theist or an Atheist and an anti-theist.
Hell, you could be a theist and an anti-theist... you'd be fucking hypocritical and retarded but still.